a) Field of the invention
This invention relates to pigment dipersants and pigment compositions using the same.
b) Detailed Description of the Related Art
Upon mixing and dispersing a pigment in a vehicle such as a paint, gravure ink or offset ink, difficulty is generally encountered in stably dispersing the pigment in the vehicle. Fine particles of the pigment, which have once been dispersed in the vehicle, tend to flocculate in the vehicle. This leads to an increase in the viscosity of the vehicle with the pigment dispersed therein, a reduction in the coloring power of an ink or paint making use of the vehicle with the pigment dispersed therein, a reduction in the gloss of a coating of the ink or paint, or the like.
An object of the present invention is, therefore, to provide a pigment dispersant, which upon production of printing inks (offset inks, gravure inks and the like), various paints, plastics, pigment-type textile printing agents, dry or wet toners for electrophotography, inks for ink-jet recording, inks for thermal transfer recording, inks for writing instruments, colorants for color filters, and the like, prevents flocculation of dispersed pigment particles and permits the production of these inks and the like with excellent flow property and high stability.
In one aspect of the present invention, there is accordingly provided a pigment dispersant (hereinafter simply called xe2x80x9cdispersantxe2x80x9d ), which comprises a compound represented by the following formula (I) or (II) or a metal, ammonium or amine salt thereof: 
wherein Xi is a hydrogen atom, a halogen atom, or an alkyl or acylamino group which may be unsubstituted or substituted by at least one atom or group selected from the group consisting of halogen atoms, alkyl groups and an acylamino group, Y1 is an anthraquinonylamino, phenylamino, naphthylamino or phenoxy group which may be unsubstituted or substituted by at least one atom or group selected from the group consisting of halogen atoms, alkyl groups and an acylamino group, R1 is a hydrogen atom or a substituted or unsubstituted alkyl or phenyl group, and R2 is a substituted or unsubstituted alkylene, phenylene or naphthylene group; or 
wherein X2 is a hydrogen atom, a halogen atom, or a substituted or unsubstituted alkyl group, R3 is a hydrogen atom or a substituted or unsubstituted alkyl or phenyl group, R4 is a substituted or unsubstituted phenyl or naphthyl group, and n means an average number of sulfonic acid groups introduced in said compound and stands for a number of from 0.5 to 2.
In another aspect of the present invention, there is also provided a pigment composition, for example, a colorant for gravure inks, paints or color filters, which comprises a pigment and the above-described dispersant.
The dispersant of the present invention is useful for dispersing various pigments, which include organic pigments and inorganic pigments, in vehicles for a variety of applications such as printing inks (offset inks, gravure inks and the like), various paints, plastics, pigment-type textile printing agents, dry or wet toners for electrophotography, inks for ink-jet recording, inks for thermal transfer recording, inks for writing instruments and inks for color filters. The dispersant of the present invention can significantly improve the flow property of inks, paints and the like, can prevent flocculation of pigment particles, and hence, can provide colored articles which show excellent gloss and vividness.
The dispersant according to the present invention features in the inclusion of a yellow to reddish purple anthraquinonylaminotriazine structure in its structure. It has excellent compatibility with various pigments, and is usable for dispersing a variety of pigments. Owing to its excellent pigment dispersing effect, the dispersant according to the present invention can also be used for the production of colorants which are useful in various applications.
The dispersant according to the present invention can be produced by a process disclosed, for example, in JP 46-33232 B, JP 46-33233 B or JP 46-34518 B or by a similar process.
For example, the dispersant represented by the formula (I) can be obtained by reacting 1 mole of a substituted or unsubstituted 1-aminoanthraquinone, 1 mole of one of a substituted or unsubstituted aniline, a substituted or unsubstituted phenol or a substituted or unsubstituted 1-aminoanthraquinone, and 1 mole of cyanuric chloride at 130xc2x0 C. to 170xc2x0 C. for 2 to 6 hours in an inert solvent such as o-dichlorobenzene and further reacting 1 mole of an aliphatic or aromatic amine, which contains one sulfonic acid group per molecule, at 150xc2x0 C. to 170xc2x0 C. for 3 to 4 hours.
The dispersant presented by the formula (II), on the other hand, can be obtained by reacting 2 moles of a substituted or unsubstituted 1-aminoanthraquinone and 1 mole of cyanuric chloride at 130xc2x0 to 170xc2x0 C. for 2 to 6 hours in an inert solvent such as o-dichlorobenzene, further reacting 1 mole of an aromatic amine, which does not contain any sulfonic acid group, at 150xc2x0 C. to 170xc2x0 C. for 3 to 4 hours, and then sulfonating the reaction product with a sulfonating agent such as fuming sulfuric acid.
Examples of the aliphatic amine or aromatic amine, which contains one sulfonic acid group per molecule and is useful for the production of the compound of the formula (I), can include taurine, N-methyltaurine, o-aminobenzenesulfonic acid, m-aminobenzenesulfonic acid, sulfanilic acid, 4-chloroaniline-3-sulfonic acid, 2-nitroaniline-4-sulfonic acid, 2-aminophenol-4-sulfonic acid, o-anisidine-5-sulfonic acid, p-anisidine-5-sulfonic acid, o-toluidine-4-sulfonic acid, m-toluidine-4-sulfonic acid, p-toluidine-2-sulfonic acid, 2-chloro-p-toluidine-3-sulfonic acid, 3-amino-6-chloro-4-sulfobenzoic acid, 1-amino-8-naphthalenesulfonic acid, 2-amino-1-naphthalenesulfonic acid, 5-amino-1-naphthalenesulfonic acid, 6-amino-1-naphthalenesulfonic acid and 5-amino-3-naphthalenesulfonic acid.
Examples of the aromatic amine useful for the production of the compound of the formula (II) can include aniline, N-methylaniline, toluidine (o-, m- or p-), anisidine (o-, m- or p-), chloroaniline (o-, m- or p-), diphenylamine, 1-naphthylamine and 2-naphthylamine.
Illustrative of the metal, which may form the metal salt with the compound represented by the formula (I) or (II), are alkali metals such as Li, Na and K; and multivalent metals such as Ca, Ba, Al, Mn, Sr, Mg and Ni. Illustrative of the amine, which may form the amine salt with the compound represented by the formula (I) or (II), are (mono, di or tri)alkylamines, substituted or unsubstituted alkylenediamines, alkanolamines, and alkylammonium chlorides.
Concerning the mixing ratio of the dispersant of the present invention to the pigment, the dispersant may be added in a proportion of from 0.05 to 40 parts by weight, preferably from 0.1 to 10 parts by weight per 100 parts by weight of the pigment. If the dispersant is added in an unduly low proportion, the intended effect of the dispersant cannot be fully brought about. Even if the dispersant is added in an excessively high proportion, the effect of the dispersant cannot be obtained so much as its proportion. On the contrary, use of the resulting pigment composition leads to paints or inks with reductions in the physical properties of their vehicles, and due to the color of the dispersant itself, the hues of the dispersed pigments are substantially modified.
Examples of pigments, the dispersion of which can be effectively achieved by the use of the dispersant of the present invention, can include organic pigments such as azo pigments, phthalocyanine pigments, quinacridone pigments, anthraquinone pigments, dianthraquinonyl pigments, isoindolinone pigments, perylene/perionone pigments, dioxazine pigments, indanthrone pigments, flavanthrone pigments, anthanthrone pigments, pyranthrone pigments, diketopyrrolopyrrole pigments, vat-dye pigments and basic-dye pigments; and inorganic pigments such as titanium oxide, carbon black, Prussian blue, ultramarine, red iron oxide, iron black, zinc white, chrome yellow and composite oxide pigments. Among these, particularly preferred are C.I. Pigment Red 245, C.I. Pigment Red 254, C.I. Pigment Red 177 and C.I. Pigment Green 36.
No particular limitation is imposed as to how the dispersant of the present invention is used. For example, the following methods can be mentioned:
1. The pigment and dispersant are mixed together beforehand by a known method, and the resulting pigment composition is added to a vehicle or the like to disperse the pigment in the vehicle or the like.
2. Upon dispersing the pigment in the vehicle or the like, the pigment and dispersant are separately added in predetermined proportions to a vehicle or the like to disperse the pigment and dispersant in the vehicle or the like.
3. After the pigment and dispersant are separately dispersed in portions of a vehicle or the like, the resulting dispersions are mixed together in predetermined proportions.
4. To a dispersion obtained by dispersing the pigment in a vehicle or the like, the dispersant is added in a predetermined proportion to disperse the pigment.
Whichever method is used, the intended pigment dispersing effect can be obtained. However, the method 1 or 2 is desired for more effective dispersion.
The pigment composition which contains the dispersant according to the present invention can be produced by mixing the pigment and the dispersant together in accordance with one of various methods known to date, and no particular limitation is imposed on its production method. Illustrative production methods can include: to mix powder of the pigment and powder of the dispersant without using any disperser; to mechanically mix the pigment and dispersant in one of various dispersers, such as a kneader, roll, or attritor; to add and mix a solution, in which the dispersant according to the present invention has been dissolved or finely dispersed, to and with a suspension of the pigment in water or an organic solvent such that the dispersant is allowed to uniformly deposit on surfaces of the pigment; and to dissolve the pigment and dispersant in a solvent having strong dissolving power such as sulfuric acid, and then to have both of the pigment and dispersant coprecipitated with a poor solvent such as water.
As is appreciated from the foregoing, the dispersant may be used in any one of solution, slurry, paste and powder forms upon preparation of the pigment composition. Whichever form the dispersant is used in, the effects of the present invention can be brought about.
Further, the dispersants according to the present invention can be used either singly or in combination and moreover, can be used in combination with one or more of conventionally known dispersants, for example, rosin, high molecular dispersants, surfactants, and pigment derivatives with polar groups introduced therein.
No particular limitation is imposed on the application of the pigment composition according to the present invention. For example, the pigment composition according to the present invention can be used as a colorant in various applications such as printing inks (offset inks, gravure inks and the like), various paints, plastics, pigment-type textile printing agents, dry or wet toners for electrophotography, inks for ink-jet recording, inks for thermal transfer recording, inks for writing instruments, and colorants for color filters. The pigment composition according to the present invention is particularly useful as a colorant for color filters in each of which a pigment is required to be dispersed to high degree.
In general, a colorant for color filters is produced by dispersing a pigment to high degree, for example, in a varnish of a photosensitive resin, such as a photosensitive polyacrylate resin, photosensitive polyamide resin, photosensitive polyimide resin or unsaturated polyester resin, or in a varnish obtained by adding a monomer as a reactive diluent to the varnish of the photosensitive resin. Use of the dispersant or pigment composition according to the present invention upon production of the colorant makes it possible to provide the colorant for color filters with high dispersion stability and high transmittance. For example, JP 10-338832 A discloses use of a pigment as a colorant for color filters by adding a pigment derivative and a cationic high molecular dispersant to the pigment. Use of the dispersant according to the present invention in place of the pigment derivative makes it possible to produce a colorant for color filters, said colorant featuring high dispersion stability of the pigment and also high transmittance.